1. Field of the Invention
The present invention relates to controlling a pitch and roll of a head in a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads write and read information by magnetizing and sensing the magnetic fields of the disk surfaces. Each head is attached to a flexure arm to create a subassembly commonly referred to as a head gimbal assembly (“HGA”). The HGA's are suspended from an actuator arm. The actuator arm has a voice coil motor that can move the heads across the surfaces of the disks.
During operation, each head is separated from a corresponding disk surface by an air bearing. The air bearing eliminates mechanical interference between the head and the disks. The strength of the magnetic field from the disk is inversely proportional to the flying height of the head relative to the disk. Reduced spacing results in a stronger magnetic field on the disk, and vice versa.
The flying height is a function of a pitch and roll of the head. It is desirable to control the pitch and roll of the head during operation to insure proper head stability. There have been developed hard disk drives that include micro-actuators to provide micro control of the head flying position. For example, there have been developed head gimbal assemblies that include a ceramic frame that supports the head. Two piezo-electric transducers are attached to the ceramic frame. Excitation of the transducers can cause lateral movement of the head. The range of lateral movement of the head is typically on the order of a few track widths.